To date, we have enrolled 18 subjects in the study. Of that number two subjects did not complete both laboratory sessions. Of the 16 subjects that completed both days, 10 showed evidence of a stimulatory effect of naloxone 125 mcg/kg. We are now in the process of retesting the six subjects who did not respond by challenging them with a higher dose of naloxone (375 mcg/kg). This refinement of the methodology will enable us to complete the initial phase of this study during the next grant year. We expect to complete retesting of the 6 nonresponders by the end of February, 1996. We will then recruit 20 new subjects over the course of 1996, which we expect to provide us with an adequate sample for data analysis. If the hypothesis is supported, we plan a second phase of the study, in which we will compare the effects of naloxone challenge with an ethanol challenge. This will enable us to determine the degree to which the effects of the opioid antagonist are comparable to the effects of ethanol in differentiating responses in subjects differentiated by family history of alcoholism.